A large body of evidence from us and others indicates that a chronic inflammatory state marked by elevated IL-6 contributes to many age-related diseases, frailty, disability and mortality in older adults. Despite this, the causes and underlying mechanisms leading to this chronic inflammatory state remain to be defined. Studies have reported clonal expansion of cytomegalovirus (CMV)-specific T cells in CMV-seropositive older persons and associations of CMV seropositivity or absolute titers with frailty, disability, ad mortality. However, ample conflict reports exist in the literature. This is because anti-CMV IgG serology is a crude measure that merely indicates prior exposure to the virus and makes no distinction between past (resolved) or chronic (persistent) infections. CMV biology indicates that while most people are exposed to the virus, CMV can persist in some with the viral genome (DNA) harbored in peripheral blood monocytes, representing a chronic infection. This application seeks to characterize CMV viral DNA in monocytes detected by a nested PCR-based assay and test the hypothesis that CMV DNA in monocytes predicts T-cell immunosenescence and chronic inflammation in older adults better than anti-CMV IgG serology. We will use an in-depth longitudinal analysis in the Women's Health and Aging Studies II, a large NIA-funded cohort study with banked peripheral blood mononuclear cells (PBMCs) and sera collected at 7 visits over 12 years. Our hypothesis is supported by our published pilot studies that only about 50%-60% of CMV-seropositive older persons had CMV DNA in monocytes and that CMV DNA (and not IgG titer) was associated with increased CMV-specific CD8 T cells and elevated serum neopterin and IL-6 levels. Preliminary data at two time points 12 years apart shows change in CMV DNA status over time in parallel with that in CMV-specific CD8 T cells and IL-6 levels, while anti-CMV IgG titer remains the same. We propose two aims: 1) To test the hypothesis that anti-CMV IgG serology does not predict the presence and change of CMV DNA in monocytes in older adults over time, and 2) To test the hypothesis that CMV DNA in monocytes is a better predictor than anti-CMV IgG serology for: a) T-cell immunosenescence as measured by expansion of CMV-specific and interferon (IFN)-g-producing CD8 T cells and terminally differentiated T-cell subsets (CD28-, CD27-, and CD45RA+), and b) elevated IL-6 and neopterin levels. The data obtained will ultimately enable us to establish a link between chronic CMV infection and both T-cell immunosenescence and chronic inflammation. If our hypotheses are confirmed, this data will open new research avenues for further studies into fundamental immunological and inflammatory mechanisms by which chronic CMV infection contributes to the development of adverse health outcomes in older adults, which will be pursued via other funding mechanisms including R01. Major health implications include fostering successful aging and maintaining function through prevention or mitigation of chronic CMV infection and its adverse impact on immunity and health for this vulnerable population.